LONDON, April 21 (Reuters) - British shares inched lower on Friday, scoring their worst weekly losses since early November after Tuesday's surprise call for an national election caused equities to fall.

The FTSE 100 fell 0.1 percent, ending the week with a fall of 2.9 percent.

Prime Minister Theresa May called the early vote for June 8, sending sterling higher and erasing year-to-date gains for the FTSE.

"The FTSE has obviously had a terrible week - although corporate earnings have been somewhat of a mixed bag, the snap election, while providing medium term stability for Brexit negotiations, has created some short term market uncertainty," said Mark Ward, head of execution trading at Sanlam Securities.

Mid-caps also fell slightly but small-caps maintained their outperformance on the day. They have gained 7.1 and 5.9 percent respectively this year.

"People have been reaching for the UK domestic stocks, but there's reasons to be quite cautious there still," said Eric Moore, head of Miton's UK Income fund.

"The UK consumer is still under the cosh. Consumption has held up quite well but it's supported by things that are unsustainable in the long run," he added.

Retail sales figures out Friday showed the biggest quarterly fall in seven years for the first quarter, as rising prices started to squeeze consumers.

Energy stocks were top weights on the FTSE as crude prices retreated, while consumer staples stocks were weakened as with Reckitt Benckiser fell 0.8 percent after its first-quarter sales disappointed due to weak markets in Europe and North America.

"While the market was prepared for a weak quarter, Reckitt Benckiser is the only EU Food/HPC company so far to miss on undemanding like-for-like expectations," said UBS analysts.

A thumbs-up from Barclays boosted Marks & Spencer shares up 1.9 percent, taking the retailer back to its pre-Brexit vote levels for the first time.

Barclays opened coverage of the stock with an "overweight" rating, saying a shift towards food, and management's plan to overhaul its clothing and home segment, would drive growth.

"We expect food to account for 64 percent of UK sales in 2020, rising steadily from 52 percent in 2010."

Merger moves continued to move stocks, and mid-cap WS Atkins rose 6.1 percent to an all-time high after Canadian engineering firm SNC-Lavalin Group firmed up its $2.67 billion offer to buy the firm.

Phone and broadband provider TalkTalk gained 4.7 percent after HSBC upgraded the stock to "buy" from "hold", saying the government's Wholesale Local Access review was good news for TalkTalk which could benefit from lower input prices.